Question

Брат старше сестры в 2 раза. Пять лет назад брат был старше сестры в 7 раз. Сколько лет брату и сестре?

Answer 1

2x + x = 21
3x = 21
x = 21 : 3
x = 7 ( сестре)
x = 7 * 2 = 14 (брату)

Ответ: сестре 7 лет а брату 14 лет.

Answer 2

Сестре 7 лет брату 14)
Решать через уравнение
2х+х=21 ( 2х так как брат сейчас старше сестры в 2 раза, х возраст сестры) 
3х=21 
(т.е. 21\3 =7) сестре 
и умножаем 7*2=14 это брату

Answer 3

Problem Analysis

We are given that the brother is 2 times older than the sister, and 5 years ago, the brother was 7 times older than the sister. We need to determine the ages of the brother and sister.

Solution

Let's assume the current age of the sister is x years. According to the given information, the brother is 2 times older than the sister, so his current age is 2x years.

Five years ago, the sister's age was x - 5 years, and the brother's age was 2x - 5 years. At that time, the brother was 7 times older than the sister, so we can set up the equation:

2x - 5 = 7(x - 5)

Now, let's solve this equation to find the value of x.

2x - 5 = 7x - 35

35 - 5 = 7x - 2x

30 = 5x

x = 6

Therefore, the sister is currently 6 years old, and the brother is 2 times older, so he is 2 * 6 = 12 years old.

Answer

The brother is 12 years old, and the sister is 6 years old.